1. Field of the Invention
The present invention relates to a cleaning blade that is employed in a cleaning device of an image forming apparatus, such as electrostatic copying machines, printers, and facsimile apparatuses, and is used for eliminating remaining toner from a surface of an image-holding member by pressure-contact thereto.
The present invention also relates to an apparatus employing the cleaning blade.
2. Related Background Art
In a known image forming apparatus, in which transferable toner images formed on an image-holding member are repeatedly transferred onto a transfer material, such as paper, the toner remaining on an image-holding member has to be removed completely in every transfer step. Generally the remaining toner is eliminated by pressing uniformly against the surface of the image-holding member a blade, which is made of a rubber elastomer and has a precise edge, against the surface of the image-holding member and sliding the blade on the surface. The cleaning blade is usually made of urethane rubber.
The cleaning process employing the urethane rubber, however, is disadvantageous in that the simple pressure-contact of the cleaning blade with the image-holding member causes reversal or bounding of the cleaning blade 3 of urethane rubber, which supported by supporting member 2 as shown by a dotted line in FIG. 1. The reversal or bounding is caused by the high friction coefficient of the urethane rubber material, which results in strong friction between the urethane rubber and the image-holding member. Thus, the remaining toner is not completely removed.
For this reason, various measures have been investigated and tired. For example, the tip of the cleaning blade made of polyurethane rubber or the surface of the photosensitive member may be covered with a lubricating fine powder or the like of a fluorine type resin, such as polyvinylidene fluoride and polytetrafluoroethylene, to reduce the amount of friction between the urethane rubber and the photosensitive member at an initial sliding stage. Such lubricating fine powder must be applied uniformly in a minimum amount since excessive application deleteriously affects the image due to its electric characteristics. However, such application is not easy technically, and still involves reliability problems with respect to the reversal or bounding of the blade caused by non-uniform coating.
Another problem is that, during repetition of the cleaning process, the lubricating fine powder maybe scattered and lost from the vicinity of the edge, thus reducing its lubricating effect. The toner, which then comes instead to play the role of the lubricating powder instead, provides a less friction-reducing effect. As a result the urethane blade tends to scatch or abrade the photosensitive member and shorten the life thereof, especially when the photosensitive member is an organic photosemiconductor.
Morever, when a urethane rubber material is used for such a cleaning blade, a casting type thermosetting liquid urethane is usually used to prepare the blade because of abrasion resistance of this material with respect to the photosensitive member. Further, this type of material is less likely to contaminate the photosensitive member, the toner and the like as a result release by the urethane rubber of an exudate. This type of urethane material, however, requires a long reaction time for heat cure, and is highly reactive to moisture in the atmosphere, thus involving problems in production equipment cost, and control of the material quality. Accordingly, a production process free from such problems are desired.